1. Field of the Invention
The present invention relates to intra-aortic balloon pumps ("IABP") that act as a left ventricular assist device ("LVAD"). More particularly, the present invention relates to a cooperatively acting dual balloon system wherein one balloon is located inside the aorta and a second balloon is located outside the body, a hollow catheter allowing for blood communication between the second balloon and the aorta.
2. Description of the Prior Art
The intra-aortic balloon pump ("IABP") is by far the most commonly utilized left ventricular assist device ("LVAD"). This device is used when the patient's cardiac output is not sufficient to maintain an adequate blood pressure for supplying the patient's organs with arterial blood.
The IABP consists of an inflatable balloon attached to a catheter, which is advanced through the patient's femoral artery and into the descending aorta. Inflation and deflation of the balloon is accomplished by an external control unit synchronized with the heart beat. This unit rapidly inflates the balloon during the diastolic or resting phase of the heart cycle, and thus elevates diastolic aortic blood pressure and improves blood flow to the heart, the brain and other tissues. The balloon is rapidly deflated as the heart contracts. This reduces the aortic blood pressure that the heart must overcome to eject blood from the left ventricle. Thus, the IABP is a LVAD that also augments diastolic aortic blood pressure.
However, present IABP devices cannot sustain the circulation if the heart is severely diseased or injured, since ventricular ejection must be sufficient to keep the mean aortic blood pressure above approximately 60 mmHg. When the aortic pressure falls below this value, there is insufficient blood to fill the space around the balloon when it is deflated. In that case the wall of the aorta collapses around the deflated balloon of prior art devices, and the IABP becomes ineffective. Thus, present IABP devices can be used only in less severe cases of left ventricular failure.
The present invention is directed towards improving the usefulness of IABP devices by enhancing the use of a single balloon in the descending aorta with a second, external balloon located outside the body and in direct communication with the blood within the aorta through a hollow catheter tube connecting both balloons. Although several IABP devices have used multiple balloons to enhance circulation, none use an external balloon working cooperatively with the internal balloon. Gabbay (U.S. Pat. No. 4,527,549) discloses the use of a balloon within the ascending aorta and multiple smaller balloons within the aortic arch and descending aorta. Given the difficulty in positioning a balloon within the ascending aorta with a catheter coming up from the descending aorta, the Gabbay device is cumbersome and difficult to operate. More importantly, the Gabbay device has the disadvantage of being positioned in the ascending aorta in order to function, thus increasing the chance of producing emboli that can cause problems such as stroke. Choy et al. (U.S. Pat. No. 4,902,273) discloses a dual balloon device, but which operates by a completely different mode. In the Choy et al. device, one balloon enters the left ventricle of the heart and another balloon enters the right ventricle of the heart. In a diseased heart, which may already be dilated, this would excessively expand the ventricle and may cause rupture or other permanent damage. Positioning the balloons in that invention is also cumbersome, making the device impractical for many applications.
Thus, what is needed is a IABP that has greater pumping capacity, that is simple to use and capable of rapid insertion and operation in an emergency situation, and that is capable of elevating blood pressure within the ascending aorta even if the descending aorta should collapse around the internal pumping balloon. The present invention is directed towards such a device.